In recent years, there have been widely developed electronic devices using organic semiconductor materials. Reports have been made on development of organic EL (Electro-Luminescence), organic TFT (Thin Film Transistor), organic semiconductor laser, etc. as light emitting devices. Out of these, particular attention is paid to the organic TFT, a type of organic transistors, as a technology for forming integrated circuits on glass or plastic substrates at low cost.
With respect to the structure of the organic TFT, Japanese Patent Laid-Open Nos. 08-228034, 09-232589, 10-270712, etc. propose the devices having the source/drain electrodes and the gate insulating film, and the gate electrode.
It has been pointed out that the organic semiconductor shows a small mobility compared to Si semiconductors and cannot follow a high frequency. In order to improve this point, attempts are made to enhance the mobility by improving crystallinity of the organic semiconductor (C. Dimitrakopoulos et. al., Science, Vol. 283 (1999), P. 822), excessively shorten the gate length (J. H. Schon et. al., Nature, Vol. 413 (2001), P. 713), and the like.
However, any of these attempts necessitates complicated processes, leaving problems in the low cost strategy.